Well drilling fluids and methods of use



Patented. Jan. 2, 1951 WELL DRILLING FLUIDS AND METHODS OF USE Gary R.Wagner, Utlca, Ohio, assignor to Phillips Petroleumcompany, acorporation 01' Delaware No Drawing. Application August 15, 1947, SerialNo. 768,943

18 Claims.

This invention relates to water base drilling muds containing a watersoluble salt of a carboxyalkylcellulose selected from the groupconsisting of ammonium carboxymethylcellulose, alkali metalcarboxyethylcellulose, alkaline earth metal carboxyethylcellulose, andammonium carboxyethylcellulose wherein the important alkali metals arelithium, sodium and potassium and the important alkaline earth metalsare magnesium, calcium, strontium and barium. In some aspects it relatesto drilling fluids suitable for drilling in heaving shale. In stillother aspects it relates to drilling fluids having a high salt content,due either to deliberate addition of salt, or due to contamination ofthe mud with salt from natural formations or from connate waters. Italso relates to methods of drilling or controlling wells with suchfluids. It is a companion invention to my copending application SerialNo. 549,299, filed August 12, 1944, now U. S. Patent 2,425,768 forDrilling Fluids and Methods of Use."

In the art of drilling wells, especially drilling by the rotary method,it is necessary to use a drilling mud, as is well understood in the art.The drilling mud lubricates the drill stem, carries the cuttings to thesurface of the well, and forms a filter cake on the walls of the wellpreventing loss of at least any substantial amount of water from thedrilling mud to the natural formations in the well. The weight of themud prevents blowouts of formation pressures especially when weightingagents are employed. In order to perform these important functionsproperly the drilling mud must havesuitable viscosity and otherqualities at all times in spite of adverse conditions encountered indrilling the well. Thixotropic properties of the mud support thecuttings during any time the pumps are shut down. I

In drilling wells there are two major difllculties caused by naturalformations penetrated. The

first of these difficulties is that if salt is encountered the salt willcut ordinary drilling mud so that its viscosity is entirely too high,the clay particles are deflocculated, and there is grave danger of thedrilling pipe twisting in half or gas cutting or a blowout occurring dueto the salt cutting of the mud. The other difliculty en-' countered isthat when a formation known as heaving shale is penetrated, this heavingshale absorbs water from the drilling mud and by a caving ordisintegration action common to clay and shale, or by a swelling actioncommon to.

bentonite materials, the well hole is closed around the drill stringchoking off the circulation of drilling mud and often seizing the drillstrin so that the drill string twists in half.

The principal object of my invention is to produce a drilling mud whichcan be used not-only in ordinary-formations but which will resistcontamination by salt and which will not cause heaving shale or similarformations to cave or swell. 1 Another object is to provide an improveddrilling mud.

A further object is to provide a drilling mud containing a water solublesalt of a carboxyalkylcellulose selected from the group consisting ofammonium carboxymethylcellulose, alkali metal carboxyethylcellulose,alkaline earth metal carboxyethylcellulose, and ammoniumcarboxyethylcellulose wherein the important alkali metals are lithium,sodium and potassium and the important alkaline earth metals aremagnesium, calcium, strontium and barium.

Another object is to provide a drilling mud containing such a watersoluble salt of carboxyalkylcellulose and asalt.

Numerous other objects and advantagesof the invention will 'be apparentto those skilled in the art upon reading the following specification andthe accompanying claims.

agent in a drilling mud a water soluble salt of a carboxyalkylcelluloseselected from the group consisting of ammonium carboxymethylcellulose,

alkali metal carboxyethylcellulose, alkaline earth metalcarboxyethylcellulose, and ammonium carboxyethylcellulose wherein thealkali metals are lithium, sodium and potassium and the importantalkaline earth metals are magnesium, calcium, strontium and barium. Theamount of these water soluble salts of carboxyalkylcelluloses employedis not critical as even small amounts give a corresponding smallereffect,'from one to five pounds per barrel (42 gallons) being preferred,but as this depends on the formation being drilled much less or muchmore of the water soluble salts of carboxyalkylcellulose may be employedand still the advantages of my invention will be achieved to a greateror lesser extent, so that it is believed better to claim the truelimits, the lower limit being that which reduces the water loss and theupper limit being mud cannot be circulated in the well by the mudimportant 1 1 pump (which mud pump is a well known element of all rotarydrills).

Ammonium carboxymethylcellulose has long been known as an article ofcommerce. but would not seem at first to be suitable as a drilling mudadditive, because C. J. Brown and A. A. Houghton in the Journal of theSociety of Chemical Industry 60, 2548 (1941) on page 255, flrst twolines, stated it was unstable and that it loses ammonia on heating to50-60" C. It is an unexpected and patentable discovery, however, that inmany instances ammonium carboxymethylcellulose can be used successfullyin drilling mud as will be discussed below. The preparation of variouscarboxymetlwlcelluloses was described in said Brown and l-Ioughtonarticle, and the preparation of various carboxyalkylcelluloses wasdescribed in German Patent 332,203 of 1918. However, whilecarboxymetbylcellulose was easily made with cellulose, water, causticsoda, and the sodium salt of monochloroacetic acid, attempts to makecarboxyethylcellulose and carboxypropylcellulose in commercialquantities by the use of chloropropionic acid and homologs provednegative. It is preferredto produce the alkali metal, ammonium andalkali earth metal salts of carboxyethylcellulose valuable in drillingmud (or, as sometimes called, carboxyethycellulose ethers) from water,cellulose, caustic soda and acrylonitrile by the method set forth in thecopending application of William M. Hutchinson, Serial No. 729,199,filed February 17, 1947 (now Patent No.

2,619,249 dated August 15, 1950), which produces thecarboxyethylcellulose known as beta carboxyethylcellulose ether.

As reported below the alkali metal, ammonium. and alkali earth metalsalts of carboxyethylcellulose were found to be valuable as predicted bythe present inventor.

duced. In this respect the reaction to finally produce the water solublematerial may be carried 1 out in the mud pit, or even the well bore ofthe well being drilled, as carboxymethylcellulose which is an acidand isinsoluble in water may be added to the drilling mud in the pit orelsewhere, and sufficient alkali, such as ammonium hydroxide, addedto-make the desired water soluble salt of carboxymethylcellulose. Thesame is true of the formation of water soluble salts of carboxyethylcellulose.

The water soluble salts of carboxyalkylcellulose may be in died powderform, the particle size not being critical. However, for rapid solutiona particle size where 95% will pass an 80 mesh screen is useful. In thecase of some slowly water soluble salts of carboxyalkylcelluloses, or tospeed up the solution of any water soluble salts of carboxyalkylceluose,any suitable wetting agent may be The corresponding metal or ammoniumsalts of both carboxyethylcelluloses diluted mixture to the drilling mudin the mud pit or at the pump intake.

In rotary drilling the usual methods consist in adding the water solublesalts of carboxyalkylcellulose powder (which may be added to the drillifluid flowing in the mud ditch to the pump intake; or to the mud pit) byscattering the powder over the surface of the drilling mud. Analternative method would be to make up a more or less concentratedsolution of the water soluble salts of carboxyalkylcellulose and addthat in a stream to the drilling mud. In some instances a pure mixtureof water and water soluble salts of carboxyalkylcellulose may be used asthe well drilling or well controlling fluid, but mud is generally added.The drilling fluid containing the water soluble salts ofcarboxyalkylcellulose and water is pumped in circulation or reversecirculation in the drill string or used to fill or partially fill thewell in the usual operations of well drilling and well controlling ofthe prior art. When these water soluble salts of carboxyalkylcelluloseare so used in suflicient amount a new result is achieved in that saltwater does not cut the mudqualities enough to harm it for drilling andformations exposed to it do not cave or heave enough to stop thedrilling. Suitable control or mud treating agents may be used, such asphosphates and/or quebracho if desired.

1 have found that water soluble salts of a carboxyalkylcelluloseselected from the group consisting of ammonium carboxymethylcellulose,alkali metal carboxyethylcellulose, alkaline earth metalcarboxyethylcellulose, and ammonium carboxyethylcellulose wherein theimportant alkali metals are lithium, sodium and potassium and theimportant alkaline earth metals are magnesium, calcium, strontium andbarium give excellent results in water base drilling mud as statedherein, all having quite similar effects on water base mud.

Any'use of a water soluble salt of a carboxyalkylcellulose selected fromthe group consisting of ammonium carbcxymethylcellulose, alkali metalcarboxyethylceilulose. alkaline earth metal .carboxyethylcellulose, andammonium carboxy- \ethylcellulose wherein the important alkali The modeor theory of operation by which these water soluble salts ofcarboxyalkylcelluloses protect the surface of clay or bentonite fromattack by water is obscure, but it is believed that as the waterattempts to enter the clay they form a layer of a protective material onthe outside of added first, such as alcohol, or alkaline solutions,

the clay or bentonite preventing the clay, or bentonite from absorbingthe water from the drilling mud.

Drillingmuds containing'water soluble salt of a carboxyalkylcelluloseselected from the group consisting of ammonium carboxymethylcellulose.alkali metal carboxyethylcellulose, alkaline earth metalcarboxyethylcellulose, and ammonium carboxyethylcellulose wherein theimportant alkali metals are lithium, sodium and potassium and theimportant alkaline earth metals are magnesium. calcium, strontium andbarium are aosaus To determine additional properties the materials beingtested. water solutions containing one percent by weight of sodium.potassium. lithium, ammonium. barium, calcium, strontium and magnesiumcarboxyethylcellulose were prepared and the viscosity, insoluble gelcontent, and the pH of these solutions were determined. The insolublegel content was determined by centriiuging 10 ml. of 1% solutions forminutes and measuring the volume of gel in the bottom of the tube. Thealkali metal salts of carboxyethylcellulose gave as good. it not better,water loss properties than did the alkali metal salts oicarboxymethylcellulose tor the three base muds. These salts oicarboxyethylcellulose also imparted better viscosity properties to thebase muds than did the corresponding salts of carboxymethylcellulose inlow and high calcium fresh water muds. although the salts ofcarboxymethylcellulose gave lower viscosities in salt water mud. The gelstrengths, initial and ten minute. eilected by the addition of thesesalts of carboxyethylcellulose to the standard muds were, in most cases,as good as those obtained by the addition of corresponding salts ofcarboxymethylcellulose.

A sample of sodium carboxyethylmannitol was tested in low calcium mud.Because 01 its ineffectiveness in control oi water loss, no additionaltests were made on the product.

A sodium salt of carboxyethylcellulose has been prepared that willcompare very favorably with sodium carboxymethylcellulose as a drillingmud additive and that appears to have better properties, than sodiumcarboxymethylcellulose, particularly in regard to reduction in waterloss, in high calcium muds.

Table II.--Sodium carbozyethulcellulose in low calcium EB-IOF mud CEOadded lbs. per bbl 0 m 'a o'o's al ae.

9' gas...

Table IIL-Sodium carboxyethylcelhdose in high calcium EB-I 0F mud TableIV.Sodium carboxuethylcellulose in salt water EB-IOF mud (Cl-= 5.200 P.P. M.)

CEC added lbs. per bbl 0 l 2 3 4 Viscosity cps 28 26. 5 21 i6 22. 5Initial el strength, g..... 50 30 is o o min. gel strens v m- 05 60 4525 5 Water 1058, ml. in 30 min- 60 50 36. 5 l5 7 Cake thickness, in %4"564 %4 ,h 564 pl! 7.9 8.4 8.6 8-7 9.1

. boxyethylcellulose.

8 Table V.-l.'flect of carbocuethulmannitol on low.

calcium 58-101 mud GEM added, lbs. per om o l a s 4 Mud weight, lbs. peri 11.2 Viscosity cps 24 32 36.5 46 41 tial el mama 45 61 19 12 10 min 51so no no Waterioss,ml last 23 no as 24.5 no Cake t 96c '96 K1 its pH 9.0so 9.2 0.2 9.4

- Table VL-Tests made on 1% solutions of carboxuethylcellzaose as... s"rats. n

co 68 I? Die p Sodium ca'c 11.1 0.0 0.4 Sodium cMc 16.6 0.0 7.2 SodiumCarboryethylmannitol.....

' EXAMPLE C In order to show substantial equivalence of the ammonium,alkali metal and alkaline earth metal salts of carboxyethylcellulose thefollowing drilling mud tests were performed:

Water base well drilling mud evaluation tests were carried out onsamples of ammonium, magnesium. calcium and barium derivatives of car-Tests were also run on a sample of acid carboxyethylcellulose and thesample of sodium carboxyethylcellulose from which the above derivativeswere prepared.

The samples were tested in a laboratory prepared drilling mud designatedas low calcium EB-lO-F which had the following composition afterdilution; Ezmex (a native West Texas clay) 8.10%. bentonite 0.80%. B880426.30%. BaCO: 0.80% and water 57.00%.

Dosages oi the materials tested and a low visccsity grade of sodiumcarboxymethylcellulose were made so that 0. l. and 3 pounds of additivewere present per barrel of mud. The required amounts of material werehydrated in 50 ml. of water. added to 250 ml. of base mud and stirredfor 30 min. on a high speed mixer. The treated mud samples were allowedto stand overnight then stirred again for 30 min. and tested {orviscosities. gel strengths and water losses according to the testprocedures outlined in A. P. 1. Code #29. These results are shown inTable VII.

After the above tests were made the mud samples containing ammoniumcarboxyethylcellulose. sodium carboxyethylcellulose, acidcarboxyethylcellulose. and the sample containing no additive wereheated, in sealed containers, at 210 F. for 2 hours. cooled to roomtemperature and again tested. The results of these tests are shown inTable VIII.

Heating at 210 F. for 2 hours improved the treating properties 01' bothammonium carboxyethylcellulose and acid carboxyethylcellulose whilesodium carboxyethylcellulose was apparently unaiiected. This occurspossibly because both ammonium carboxyethylcellulose and acidcarboxyethylcellulose may tend to be converted to sodiumcarboxyethylcellulose at elevated temperatures. The treating eiiectwould then be expected to approach that of sodium carboxyethylcellulose.

Table VIII shows that viscosities, gel strengths. and water losses arereduced when ammonium and acid carboxyethylcellulose treated mud 1samples are heated.

not subject to injury by salt to any detrimental degree but may still beuseful as drilling muds when there is as much in some instances as238,000 parts per million of sodium chloride in the drilling mud ormore. Such muds containing these water soluble salts ofcarboxyalkylcellulose often have low initial gel strength which allowsgas bubbles to come out of the drilling mud so rapidly that the drillingmud will not become gas cut; Elimination of gas cutting reduces thechances of blowouts. Water soluble salts of a carboxyaikyicelluloseselected from the group consisting of ammonium carboxymethylcellulose,alkali metal carboxyethylcellulose. alkaline earth metalcarboxyethylcellulose, and ammonium carboxyethylcellulose wherein theimportant alkali metals are lithium, sodium and potassium and theimportant alkaline earth metals are magnesium, calcium, strontium andbarium drilling muds are often characterized by very thin filter cakethickness and by very small water loss or complete absence of waterloss. This is very .useful in avoiding loss of water to the formation,as well as the resultant swelling or caving of the formation whichoccurs with some formations. They do not generally ferment or spoil.Numerous other advantages of such drilling muds will be apparent from astudy of the following representative experiments which have beenselected to show in a minimum of space the advantages of water solublesalt of a carboxyalkylcellulose selected from the group consisting ofammonium carboxymethylceliulose, alkali metal carboxyethylcellulose,alkaline earth metal carboxyethylceilulose,

viscosity measurements were all made with a Stormer Viscoscirneter 1931model made by Arthur H. Thomas Company. The mixing of samples was alwaysfor minutes with a Hamilton Beach No. 33 high speed mixer. Sodiumchloride content was calculated from a determination of the chlorineions by titration with silver nitrate using a potassium chromateindicator. The filter cake thickness and water losses were alldetermined with an A. P. 1. low pressure wall buiding tester filterpress with a pressure of 100 lbs. per square inch applied for minutes.All temperatures were approximately room temperature. All barrels are 42U. 8. gallon barrels.

EXAMPLE A Three different laboratory base muds were used in evaluatingthe samples of carboxyethylcellulose and-carboxyethylmannitol, a'lowcalcium. fresh water EB-10F mud, a high calcium, fresh water EB-lOF mud,and a high calcium, salt water mud. In each mud there was a 10 to 1weight ratio of Ezmex clay to bentonite, a total clay content around12%, and suflicient B8304 to weight the muds to around 11-12 pounds pergal. The EB-lO mud was treated with 1% BaCO: (or phosphates) to give thelow calcium mud, it was used unchanged to give the high calcium mud, andit was treated with sodium chloride (5 saturated) to give the salt watermud. Muds varying slightly in composition and treatment were usedthrough this extended investigation. This is shown in the following andammonium carboxyethylceliulose wherein table.

Table I.Composition of mud: used in investigation Composition of the MudI cEgggple at g? Per cent Per cent Per cent bz' g P M igil?Addmomielggld Treat.

7 Clay Baco. Baso. H10 C800, 8

Low CALCIUM MUD HIGH CALCIUM MUD 1s 12 30 as 2, 100 12 SALT WATER MUD 1511 1 so as 1, 445 65,200 11.9

' 1 Base mudsdilutedtospartsbasemudtoipart tives. Properties of mudsgiven in later tables are for the important alkali metals are lithium.sodium and potassium andthe important alkaline earth metals aremagnesium, calc barium drilling muds.

TESTS ium, strontium and The tests of the properties of solutions ofthese water soluble salts of carboxyalkylcelluloses and/or drilling mudswere all made with standard drilling mud laboratory equipment.

The measurements of pH were all made with a Beckman Industrial Model M"additional water in tests. Dilution due to water solutions of addithediluted muds.

nxammn In making the tests on the muds, quantities of the samples ofcarboxyethylcellulose and carboxymethylmannitol equivalent to 1, 2, 3,and 4 pounds per barrel were dissolved in the laboratory prepared muds.Each treated mud sample was stirred for ,30 minutes on a high speedelectric mixer and then tested for viscosity, gel strength, water loss,cake thickness and pH. Standard test equipment and procedures as out pHmeter. The lined in A. P. 1. Code 29 were used.

Table VIL-Comparison of eflccts of CEO derivatives and sodiumcarbozumethulcellalose on EB-1 -1 low calcium mud Viscosity, cps. gg f 3g pHofFiltrate Poundsperbarrel 0 l 3 0 3 0 1 3 0 1 3 0 l 3Bodiummrboxymethylcellulosa. 29 25 55 31 o o 45 1119 1119 31.5 1 4.5 9.23.9 9.1 NmcEc 2o 25 35 31 25 o 45 50 31.5 34 1.5 9.2 9.0 3.9 MgCE 29 919.5 31 2 o 45 25 o 31.5 as 1115 9.2 9.0 :13 090E 29 24.5 32 31 25 o 4545 15 31.5 32.5 1.5 9.2 3.9 119 1350110-- 29 25.5 30 31 2o 0 45 3o 2031.5 33 a 9.2 9.0 119 mono..." 20 13.5 35 31 o 2 45 5 31.5 11 5 9.2 9.93.9 moose 2o 41 15 31 5o 40 45 50 199 31.5 34 9.2 as 9.5

l Barium sulfate dropped out.

Table VIlL-Eflect of heating selected samples at 210 F. for 2 hours11111131051. 10 Min. 39min. water Viscosity, cps. gum I pH oi FiltrataPonndsperbarrel 0 l 3 0 l 3 0 l 3 0 1 3 0 l 3 193.0110 19 19 39 25 1 15o 29 19 33 4 1 '9 a1 a1 NaCEC 1a 14 425 25 2 o 59 2o 33 11 5 9 a5 a5.auacnc 1s 39 59 3s 5 5o 55 4o 33 21.5 o 9 a9 a5 EXAMPLE D TableIXProperties of 1% aqueous solutions As stated above free acidcarboxymethylcelluof cue lose and free acid carboxyethylcellulose can beused successfully in drilling mud containing ions -mg DH ml. 10 ofammonium, or ions of metals, which form 29 '0. water soluble salts ofcarboxyalkylcellulose. For example, tests on carboxymethylcellulosepowder ssodmn mo 5 1.5 m.

1 ammo um t 14.6 6.0 Do. added to a dn lhng mud of pH 11 containing 0M0Free 13 U sodium hydroxide, or on a normal pH mud CMC 51 111555111 1 3.911159111111. heated to 95 0., indicate that suitable reductions inviscosity, water loss and gel strengths occur which indicate that sodiumcarboxymethylcellulose has probably been formed with the result that thewater base drilling mud is greatly improved for all drflllng purposes.

1 CMC dispersed with NaOH. Ml. insoluble gel in centrifuge tube aftercentrifuging for 5 min.

The acid and ammonium CMC were tested in the following mud systems:

The commercial use of ammonium carboxymethylcellulose and ammoniumcarboxyethyl- (1) KB-5, fresh water, normal pH cellulose in drflllng mudwould seem impossible (2) EB-lO, low calcium, fresh water, normal pH atfirst thought in view of the alleged instability (3) EB-10, low calcium,fresh water, normal at to 60 C. of these compounds as mentioned pH,heated 20 hours at 95 C. on page 255 of the Brown and Houghton article50 (4) EB-IO, low calcium, fresh water, high pH cited above, but inactual tests it was found that (5) EB-10, low calcium 50% NaClsaturated,

these compounds either were not unstable in a water base drilling mud,or else the alkali metal salts of the same were formed, so that they maybe regarded as valuable drilling mud additives even if alkali metal ionsreplace the ammonium in the compound. Instead of losing treating powerat 50 to 60 C. the treating power was sustained after heating to 95 C.for long periods of time.

One gram (dry basis) of the ammonium and free acidcarboxymethylcellulose were placed in separate beakers and mixed with 99grams of water each and allowed to stand overnight. The ammoniumcarboxymethylcellulose dispersed while the acid carboxymethylcellulosedid not disperse. To disperse the acid carboxymethylcellulose, a thirdaqueous preparation was made in which alkali (NaOH) was added insuflicient amount to maintain the pH of the solution at thethymolphthalein blue end point. When the acid carboxyrnethylcellulosewas dispersed, the solution was neutralized with HCl and made up to 100ml. The properties of these 1% aqueous solutions are shown in Table IX,

high pH Table X-Weight per cent composition of mud:

China Ea- Ben- Mud clay m l mum B13805 B11605 K30 KB-li l4. 6 2. 9 i7. 566 E1340, high calcium 8. 8 0.9 26.3 64 EB-lO, low calcl 8.1 0.8 26.30.8 M

I A native Tom clay containing soluble calcium minerals.

The salt water muds were prepared by 50% saturation of the water phaseof the mud with ll sodium chloride, the salt being added after thecarboxymethylcellulose derivatives were present in the muds. The high pHmuds were obtained by adding ml. of a caustic and quebracho solution (50pounds each of caustic and quebracho per barrel of solution) to a 300ml. sample oi. mud after the additives were present. In a high 'pH-saltwater mud, salt contamination took place after the pH adjustment.

Testing procedures consisted of dispersing or hydrating thecarboxymethylcellulose derivatives in 50 ml. of water and after thesolutions had stood for several hours the 50 ml. portions were added to250 ml. of base mud. The mud compositions listed in Table X representthe concentrations of clays in the 250 ml. base mud diluted with 50 ml.of water containing the additives. Dosages oi. the cellulosic materialsequivalent to 0, 1, 2, 3 and 4 pounds material per barrel of mud wereadded in separate tests. Dosages were based on dry weights of materials.The treated muds, with pH adjustment and salt addition in specifiedcases, were thoroughly mixed, allowed to stand overnight, restirred forthirty minutes on a high speed mixer and tested in accordance with theprocedures outlined in A. P. I. Code 29.

In an elevated temperature experiment in. which ammoniumcarboxymethylcellulose treated muds were heated 20 hours at 95 C., thetreated muds were held at 95 C. in vented jars immersed in an oil bath.After the heating period, the muds were cooled to room temperature andstandard mud tests made.

The results of these tests, including comparative results using sodiumcarboxymethylcellulose, are given in the attached Tables XII throughXVIII The data in the attached Tables XIV through XVHI show a markedsimilarity between the eiIects of ammonium carboxymethylcellulose andsodium carboxymethylcellulose on the properties of the various drillingmuds tested. The principal difference exists in the slightly higherviscosities and gel strengths existing in the fresh water KB-5 and lowcalcium EB-lO muds using ammonium carboxymethylcellulose. In the saltwater muds and the high calcium EB- mud, viscosity and gel strengthcharacteristics are quite similar for the two additives. Water lossresults are very nearly the same for both the ammoniumcarboxymethylcellulose and sodium carboxymethylcellulose in all the mudsystems investigated. Temperature is noted to have the same effect onthe properties of muds. treated with ammonium carboxymethylcelluldse andsodium carboxymethylcellulose.

Several additional observations, made on ammonium carboxymethylcelluloseduring the course of this investigation, were as .follows:

These observations indicate a considerable stability of the ammoniumcarboxymethylcellulose in. muds at normal pH and the los 9? 12 ammoniaoccuring in a mud with a high pH does not impair the treating propertiesoi the additive. Elevated temperature of a mud with a normal pH alsodoes not appear to decompose the ammonium carboxymethylcellulose. Thiswas also confirmed in water solutions by heating a 2% aqueous solution01 ammonium carboxymethylcellulose to 95 C. in a vented flask. Noammonia could be detected at the vent with a moist litmus paper. Ammoniawas detected around C. when dry ammonium carboxymethylcellulose washeated.

It is of importance to note that the results obtained with ammoniumcarboxymethylcellulose are not in agreement with results reportedpreviously by Brown and Houghton in their article cited above, even withwater solutions.

Acid carboxymethylcellulose was, as expected, insoluble in water andupon addition to a fresh water mud at normal pH (around 8) had nofavorable treating properties (Tables XII and XIII). In the KB-5 mud(Table XII), the acid carboxymethylcellulose caused slight increases inviscosities and gel strengths but did not afiect the water filtrationrate. Aging the mud for 5 days did not change the mud properties exceptfor a lowerin of the pH. In the low calcium, EB-10 mud (Table XIII), theacid carboxymethylcellulose caused practically no change in theproperties of the base mud.

The results for acid carboxymethylcellulose in Tables XIV and XV areentirely different. In this group of tests in EB-lO mud at high pHranges, carboxymethylcellulose was as effective as ammoniumcarboxymethylcellulose or sodium carboxymethylcellulose. The lower pHvalues for the free acid carboxymethylcellulose samples indicate thatpart of the sodium ions of the sodium hydroxide used to raise the pH wasprobably used in converting carboxymethylcellulose to sodiumcarboxymethylcellulose.

Free acid carboxymethylcellulose was also as eiIective as sodiumcarboxymethylcellulose when the mud samples were heated 20 hours in anoil bath at C. at normal DH ranges. These results are shown in TableXVI. The reason [or the effectiveness of acid carboxymethylcellulose inthese tests is not quite as easy to explain as it was for higher pHvalues, since no additional ions were added which could have combinedwith the acid carboxymethylcellulose to have formed a solublederivative. Apparently the free acid carboxymethylcellulose wasconverted to a dispersible material of some kind, possibly sodiumcarboxymethylcellulose. If this is true, the sodium ions were probablyobtained from the clay of the mud.

The ammonium salt of carboxymethylcellulose produced almost the sametreating efiect in various drilling muds as sodiumcarboxymethylcellulose. No tests were made to determine the sta bilityof ammonium carboxymethylcellulose at temperatures above 95 C. andhigher pressures, but it is believed that if it did break down un-- dersuch conditions it would merely be converted to another solublederivative and still continue to be as effective as sodiumcarboxymethylcellulose.

Free acid carboxymethylcellulose was ineflfective as a drilling mudadditive at pH values below 8.5 at room temperatures. However, at pHvalues of 11 or temperatures of 95 0., acid carboxymethylcellulose isconverted to a soluble derivative which is as effective as sodiumcarboxymethylcellulose as a drilling mud additive.

' termediate strings of casings to protect the well gel strength and lowwater loss. to salt or anhydrite formations.

(2) Excellent logs can be obtained of all types of electrical bore holetests, such as the Electrolog" (a trade name) when the hole is full ofsuch drilling mud.

(3) Large savings in weighting agents (in the South Tyler 'field where a14 lb. mud is needed from 7.000 to 10,000 feet some 5,000 sacks of 100lbs. each of barium sulfate was saved in drilling a well which wasotherwise the same as another well using ordinary mud).

(4) Large savings in treating agents.

(5) when using such muds generally any in- Water loss, ml. in 30Viscosity, cps. Initial Gel. gm. 10 Min. Gel. gm. mm at 100 s pH ofFiltrate Poundsperbbl.. 0123401234012340123401234 TABLE JUL-The Effectof Ammonium and Free Acid CMC on KB-5 Mud CMC(sodiumsalt). 2245 91 100100 0 10 20 10 40 70 10013.5 6 4.2 3.6 2.6 8.6 8.4 8.5 .5 CME) (ammonium22 76 I sa 100 100 100 0 5 50 20 30 150 240 27013.5 5.2 4.0 2.7 2.5 8.68.7 8.6 8.1 CMO (FreeAcid) 2230.5 40 43 37.5 0 0 5 5 5 20 30 30 353013512513. 13. 12. 8.0 8.5 8.1 8.0 0M0 (Free Acid) (Atter120hr.) 2226.540 40 39.5 0 0 '0 0 2 20 10 20 30 2013.513. 12.512.512.7 8.6 7.8 6 7.46.7

TABLE XI1I.--The Eflect oi Ammonium and Free Acid CMC on EB-lO LowCalcium, normal pH, Mud

CMC (Sodium Salt 1717.532.5 40.5 55.5 0 0 0 45 5 5 7 5 29 8 4.5 3.2 3.692 9.1 9.1 .0 CMC (Ammonium t 1727 45 80.5 100 25 0 2 3 3 45 5 10 15 297 6 4.7 4. 9.2 8.7 9.1 9.5 9.2 CMC (Free Acid) "18.5225 22. 18.5 25 3832 30 45 60 45 29 3133 34 38 9.2 8.7 8.4 8.4 8.4

TABLE XIV.lhe Eflect of Ammonium and Free Acid CMC on EB-IO, LowCalcium, High pH, Mud

CMC (Sodium Salt) 4.5 1724 31.5 47.5 0 0 0 0 1 7 5 5 10 1022. 6.5 6 3.53. 11.5109 10.510.810. CMC (Ammonium 4.5 2036 73 103 0 0 0 1 2 7 5 7 152022.5 6.0 4.1 4.0 4.011.510.510.710.410.2 CML (FreeAcid)-- 4.5 2031.567 92. 0 0 0 .0 0 7 5 5 11 1522.5 6.5 4.0 3.5 3.8 11.510.510.11 9.9 9.7

TABLE XV.The Efleet of Ammonium and Free Acid CMC on Eli-10 Low Calcium,166,500 P. I. M. chlorides as NaCLhigh pH, Mud

OMC (Sodium Salt). W 3127.5 28 31 30 10 5 0 0 40 70 40 9 50 26.5145 7.4.610. 9.7 9.7 9.4 9.3 CMC (Ammonium Salt) 27 3122 24 29 30 22 0 0 0 4065 50 25 15 5031 14.5 7.4 4.810. 9.4 9.5 9.1 9.0 CMC (FreeAcid)-. 272921.5 23.5 28.5 30 15 0 0 0 40 15 10 5029 13 6.4 4.310. 9.3 8.9 8.9 8.9

TABLE XVI.-The Eflect oi Ammonium and Free Acid CMC on EB-lO. LowCalcium, normal pH, mud. Heated C. for 20 his.

CMC (Sodium Salt 14 22542.5 52. 101-5 16 0 0 1 1 35 10 15 20 25 4213.75.5 4.8 4. 8. 8. 8.4 8.4 CM 0 (Ammonium Saltl 1422.543 70 16 0 1 0 2 3510 10 15 25 42 8.7 6.3 4.8 4.6 8.8 8.5 8.9 8.8 8.7 CMC (FreeA(-id) 142035 55 80.5 10 0 0 0 0 35 10 10 10 20 42 9.5 5.8 4.9 4.3 8.8 8.5 8.5 8.68.7

TABLE XVIL-The Eflect of Ammonium CMC on EB-lO, High Calcium, normal pH,Mud. Calcium 1710 P. P. M. as 08.00;

CMC (Sodium S t 1311.5 9.5 20 27 22 1 0 0 0 35 35 2 0 0 58 45 14 5.5 3.8.18.181 8.18.1

7 i TABLE XVIIL-Thc Eficct oi Ammonium CMC on EB-lO 158,000 P. P M.chlorides as NaCl. normal pH, Mud

CMC (Sodium a1 .14.511.514 11.5 13 22 7 5 0 0 30 20 40 5 2 6271.554 28.512 8.2 7.5 6.16.5 5.9 CMC (Ammonium Salt). 14.512.514.5 11.5 11 22 8 4 00 30 30 45 6 2 6275. 58.5 30 10 8.2 7.5 6.0 6.8 6.8

EXAMPLE E from rock salt or bentonitic shale are unneces- The followingadvantages of drilling mud conand their cost can be Saved taining watersoluble salts of carboxyalkylcellu- 55 (6) The filter cake of Such mudsis thin loses will be found to be true, as evidenced by exggf aa gifiggg lig has low water loss in urn carb xymeth lzgfi s gi g g of sodi oy (7) These water soluble salts of carboxyal- (i) such drilling mud ismade resistant as 0 gi d i v f oiz th os t iflfer li t n ga i change inimportant qualities, such as viscosity. 60

additives, withstanding chemical and bacterial action and retainingtheir valuable treating properties.

(8) Because the sides of the hole do not tend to dissolve or cave withsuch mud hole enlargement during and after drilling is kept at aminimum. Many advantages result. A broken drill string cannot get undera ledge in case of a twist 05. The amount of cement used is reduced incementing around. a casing, and the cement tends to go around the entirecasing, and not channel by at one point. Actual caliper logs on twowells in the same formation show marked reduction in sizeand greateruniformity of hole diameter in the well in which such muds were usedover the well in which ordinary mud was used.

EXAMPLE F The following filtration tests may be made:

Table XIX Compound I Amount of Filtrute (A) i% CMC (ammonium salt) inOver 300 ml. in 40 seconds.

wet

er. (B) 1% CE (sodium salt) in water. Do. (C) 15% clay in water 46 ml.in 30 minutes. (D) A+C in water 8 ml. in 30 minutes. (E) B+C in water 10ml. in 30 minutes.

A pressure of 100 lbs. per square inch and a. standard filter paper isused in these tests.

EXAMPLE G lithium, sodium and potassium and the important alkaline earthmetals are magnesium, calcium, strontium and barium are left to standfor 6 months. Some of each are contaminated with sour mud (fermentedstarch mud) others merely exposed to the air.

The starch containing muds will all ferment and go sour, becomingiiocculated o otherwise worthless as drilling mud in a period of somedays, the contaminated ones fermenting almost at once, theuncontaminated ones fermenting several days later. None of the watersoluble salt of a carboxyalkylcellulose selected from the groupconsisting of ammonium carboxymethylcellulose, alkali metalcarboxyethylcellulose, alkaline earth metal carboxyethylcellulose, andammonium carboxyethylcellulose wherein the important alkali metals arelithium, sodium and potassium and the important alkaline earth metalsare magnesium, calcium, strontium and barium containing muds willferment, even after six months regardless of contamination and exposureto the air. It is possible some organism could attack them successfully,but they are much more resistant than starch containing muds.

EXAMPLE H A solution of 4 pounds to the barrel of water soluble salt ofa carboxyalkylcellulose selected from the group consisting of ammoniumcarboxydefined in the following claims.

16 ylcellulose, alkali metal carboxyethylcellulose, alkaline earth metalcarboxyethylcellulose, and ammonium carboxyethylcellulose wherein theimportant alkali metals are lithium, sodium and potassium and theimportant alkaline earth metals are magnesium, calcium, strontium andbarium may be used in water base drilling muds by those skilled in theart of water base drilling muds.

The alkaline earth metals are enumerated dif ferently in differentperiodic tables, but in drilling mud the grouping in J. W. MellorsModern Inorganic Chemistry .1939) Longmans Green & Co., publishers,(revised and edited by G. D. Parkes), page 118 (which lists as alkalimetals (group IA.) lithium, sodium and potassium and as alkaline earthmetals (group IIA) magnesium, calcium, strontium and barium) isconsidered best and is relied on in this invention. Beryllium isexcluded because beryllium nitrate in a basic solution containing sodiumcarboxyethylcell-ulose causes precipitation of the carboxyethylcellulosewhich indicates beryllium carboxyethylcellulose to be inferior.

It is to be understood that while a theory of operation has beenadvanced, it is not the only or necessary one, but has only beenadvanced to facilitate the disclosure. It is understood, however, thatthis invention is not limited to any theory of operation or action. Itis further obvious that various changes may be made in the detailswithout departing from the spirit of this invention, nor from the scopeof the invention as It is to be understood the invention is not to belimited to the specific details described. For example calcium salts mayform a white haze of colloidal nature in the solution and the solutionwill still be substantially a water soluble alkali metalcarboxymethylcellulose. For example the tests with treating and controlagents under Example H indicate that water soluble salt of acarboxyalkylcellulose selected from the group consisting of ammoniumcarboxymethylcellulose, alkali metal carboxyethylcellulose, alkalineearth metal carboxyethylcellulose, and ammonium carboxyethylcellulosewherein the important alkali metals are lithium, sodium and potassiumand the important alkaline earth metals are magnesium, calcium,strontium and barium are somewhat inert chemically and that all thetreating, weighting and control agents of the well drilling fluid andwell controlling fluid arts may, after asimple test for lack of obviousadverse reaction. be employed without invention in my water soluble saltof a carboxyalkylcellulose selected from the group consisting ofammonium carboxymethylcellulose,

methylcellulose, alkali metal carboxyethylcellulose, alkaline earthmetal carboxyethylcellulose, and ammonium carboxyethylccllulose whereinthe important alkali'metals are lithium, sodium and potassium and theimportant alkaline earth metals are magnesium, calcium, strontium andbarium in water is mixed with greater than the usual maximum proportionsof caustic soda,

alkali metal carboxyethylcellulose, alkaline earth metalcarboxyethylcellulose, and ammonium carboxyethylcellulose wherein theimportant alkali metals are lithium, sodium and potassium and theimportant alkaline earth metals are magnesium, calcium, strontium andbarium drilling and controlling fluids, and that with few, if any,exceptions they will be so employable. My invention is therefore to bedefined by the iollowingclaims.

Havingdescribed my invention, I claim:

1. In a process of drilling wells comprising the steps of drilling thewell with well drilling tools,

and circulating through the well during said drilling a water basedrilling mud which forms a filter cake on the wall of the well, theimprove, ment comprising incorporating in said drilling mud a free acidcarboxyalkylcellulose in an 7 amount suiilcient to be converted intosuiiieient water soluble carboxyaikyicellulose to reduce the IValkylcellulose is carboxym'ethylcellulose.

3. In a process of drilling wells comprisingthe steps of drilling thewell with well drilling tools, and circulating through the well duringsaid drilling a water base drilling mud of a pH greaterthan 10 whichforms a filter cake on the wall of the well, the improvement comprisingincorpo-' rating in said drilling mud' a free acid carboxyallwlcellulosein an amount sufilcient tobe converted into sufllcient water solublecarboxyalkylcellulose to reduce the water loss due to filtration throughsaid filter cake but insumcient' to increase the viscosity of saiddrilling mud to such an extent that it cannot be circulated.

4. The process of claim 3 in which the carboxyalkylcellulose iscarboxymethylceilulose.

5. A water base well drilling mud comprising in combination withsufiicient water to maintain the mud as a fluid, suificient clayeymaterial to form a filter cake on the wall oi the well, and a watersoluble salt of a carboxyalkylcellulose selected from the groupconsisting oi ammonium carboxymethylcellulose, ammoniumcarboxyethylcellulose, sodium carboxyethylcellulose, potassiumcarboxyethylcellulose, lithium carboxyethylcellulose, calciumcarboxyethylcellulose, strontium carboxyethylcellulose, bariumcarboxyethylcellulose, and magnesium carboxyethylcellulose in an amountsufiicient to reduce the water loss due to filtration through saidfilter cake without increasing the viscosity of said well drilling mudto such an extent that it cannot be circulated.

6. A water base well drilling mud comprising in combination sufllcientwater to maintain the mud as a fluid, sufiicient clayey material to forma filter cake on the wall of the well, and a water soluble ammoniumcarboxymethylcellulose in an amount sufiicient to reduce the water lossdue to filtration through said filter cake without increasing theviscosity of said well drilling mud to such an extent that it cannot becirculated.

'7. A water base well drilling mud comprising in combination sufiicientwater to maintain the mud as a fluid, sufiiclent clayey material to forma filter cake on the wall of the well, and a water soluble sodiumcarboxyethylcellulose in an amount sum'cient to reduce the water lossdue to filtration through said filter cake without increasing theviscositv of said well drilling mud to such an extent that it cannot becirculated.

8. A water base well" drilling mud comprising in combination sufilclentwater to maintain the mud as a fluid, sumcient clayey material to form afilter cake on the wall of the well, and a. water soluble alkali metalcarboxyethylcellulose in an amount suiilcient to reduce the water lossdue to filtration through said filter cake without increasing theviscosity oi' said well drilling mud to such an extent that it cannot becirculated.

9. A water base well drilling mud comprising an aqueous fluid mixturecontaining suspended solids which form a filter cake on the wall of thewell, and a water soluble salt of a carboxyalkylcellulose selected fromthe group consisting of ammonium carboxymethylcellulose, ammonium.

carboxyethylceliulose, sodium carboxyethylcellulose, potassiumcarboxyethylcellulose, lithium 'carboxyethylcellulose, calicumcarboxyethylcellu lose, strontium carboxyethylcelluiose, bariumcarboxyethylcellulose, and magnesium carbcxyethylcellulose in an amountsuilicient to reduce the water loss due tofiltration through said filtercake without increasing the viscosity of said well drilling mud to suchan extent that it cannot be circulated.

10. A waterbase well drilling mud comprising an aqueous fluid mixturecontaining suspended solids which form a filter cake on the wall of thewell, and a water soluble ammonium carboxymethylcellulose in an amountsufilcient to reduce the water loss due to filtration through saidfilter cake without increasing the viscosity of said well drilling mudto such an extent that it cannot be circulated.

11. A water base well drilling mud i an aqueous fluid mixture containingsuspended solids which form a filter cake on the wall of the well, and awater soluble sodium carboxyethylcellulose in an amount suificient toreduced the water loss due to filtration through said filter cakewithout increasing the viscosity of said well drilling mud to such anextent that it cannot be circulated.

12. A water base well drilling mud comprising an aqueous fluid mixturecontaining suspended solids which form a filter cake on the wall of thewell, and a water soluble alkali metal carboxyfiltration through saidfilter cake without increasing the viscosity of said well drilling mudto such an extent th'atit cannot be circulated.

14. A water base well drilling mud comprising in combination suiiicientwater to maintain the mudas a fluid, sufilcient clayey material. to forma filter cake on the wall of the well, and a water soluble potassiumcarboxyethylcellulose in an amount, suilicient to reduce the water lossdue to filtration through said filter cake without increasin theviscosity of said well drilling mud to such an extent that it cannot becirculated.

15. A water base well drilling mud comprising in combination sufilcientwater to maintain the mud as a fluid, sumcient clayey material to form afilter cake on the wall of the'well, anda water soluble calciumcarboxyethylcellulose in an amount sufilcient. to ,reduce the water lossdue to filtration through said filter cake without increasing theviscosity of said well drilling mud to such an extent that it cannot becirculated.

16. A water base well drilling mud comprising an aqueous fluid mixturecontaining su pended solids which form a filter cake on the wall oi thewell, and a water soluble ammonium carboxyethylcellulose in an amountsufiicient to reduce the water loss due to filtration through saidfilter cake without increasing the viscosity of said well drilling mudtosuch an extent that it cannot be circulated.

17. A water base well drilling mud comprising an aqueous fiuid mixturecontaining suspended solids which form a filtercake on the wall of thewell, and a water soluble potassium carboxyethylel ulose iii an amountsufiicient to reduce the 19 water loss due to filtration through saidfilter cake without increasing the viscosity of said well drilling mudto such an extent that it cannot be circulated.

18. A water base well drilling mud comprising an aqueous fluid mixturecontaining suspended solids which form a filter cake on the wall of thewell, and a; water soluble calcium carbo'ziyethylcellulose in an amountsumcient to reduce the water loss due to filtration through said filtercake without increasing the viscosity of said well drill- 10 Number ingmud to such an extent that it cannot becirculated.

CARY R. WAGNER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date 2,425,768 Wagner Aug. 19, 194!

1. IN A PROCESS OF DRILLING WELLS COMPRISING THE STEPS OF DRILLING THEWELL WITH WELL DRILLING TOOLS, AND CIRCULATING THROUGH THE WELL DURINGSAID DRILLING A WATER BASE DRILLING MUD WHICH FORMS A FILTER CAKE ON THEWALL OF THE WELL, THE IMPROVEMENT COMPRISING INCORPORATING IN SAIDDRILLING MUD A FREE ACID CARBOXYALKYLCELLULOSE IN AN AMOUNT SUFFICIENTTO BE CONVERTED INTO SUFFICIENT WATER SOLUBLE CARBOXYALKYLCELLULOSE TOREDUCE THE WATER LOSS DUE TO FILTRATION THROUGH SAID FILTER CAKE BUTINSUFFICIENT TO INCREASE THE VISCOSITY OF SAID DRILLING MUD TO SUCH ANEXTENT THAT IT CANNOT BE CIRCULATED.